11B Quadrupole Coupling Constants in Solid Boron Halides

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Abstract
The 11B nuclear quadrupole coupling constants have been measured in the solid boron halides and found to be 2.64 MHz in BF3, 2.54 MHz in BCl3, 2.46 MHz in BBr3, and 2.40 MHz in BI3. These values do not agree with calculated values based on descriptions of the boron–halogen bonds obtained from quadrupole coupling studies of the halogen nuclei. The discrepancy is attributed to the inadequacy of some assumptions used in the Townes and Dailey method for the case of boron. A fine structure was observed on the B11 nuclear magnetic resonance in BF3 and is completely explained in terms of a dipole–dipole interaction between the boron nucleus and the three neighboring fluorine nuclei.